Guava Leaf Extract as a Sustainable Preservative Alternative in Semi-Solid Pharmaceuticals: Efficacy and Stability Assessment

<b>Background</b>: Natural alternatives are becoming more popular as a result of health risks associated with synthetic preservatives in pharmaceuticals. Because of its antibacterial properties, <i>Psidium guajava</i> (L.) leaf extract is a practical choice for sustainable preservation. <b>Objectives</b>: The aim of this research is to evaluate the efficacy of <i>Psidium guajava</i> (L.) leaf extract as a 10% (<i>w</i>/<i>w</i>) natural preservative in five different base formulations: creams (clotrimazole cream, permethrin cream, and gentamicin cream) and gels (indomethacin emulgel and ibuprofen gel). <b>Methods</b>: Over the course of 28 days, antimicrobial activity against <i>Pseudomonas aeruginosa</i>, <i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Aspergillus brasiliensis</i>, and <i>Candida albicans</i> was evaluated. In accordance with USP/BP guidelines, three months of accelerated conditions (40 ± 2 °C/75% ± 5% RH) were used to assess chemical, physical, and microbiological stability. The stability of the active component was examined using HPLC. <b>Results</b>: Our findings showed that the extract completely inhibited the growth of tested bacterial species in clotrimazole cream, permethrin cream, gentamicin cream, and indomethacin emulgel, demonstrating significant antibacterial activity across all formulations. However, the antifungal activity was restricted. The preservation effectiveness criterion (bacterial/yeast counts < 10 CFU, mold < 20 CFU) was only fulfilled by ibuprofen gel and clotrimazole cream. Although there were color changes, stability tests verified that the active components such as ibuprofen (reduced from 97.5% to 92%) and clotrimazole (reduced from 99.9% to 95%) decomposed minimally and had acceptable physical characteristics. Particularly against fungus, the extract was surpassed by chemical preservatives (methyl/propyl paraben). <b>Conclusions</b>: Certain semi-solid pharmaceuticals can benefit from the stability and antimicrobial protection provided by guava leaf extract, a natural preservative. The weak antifungal activity of the guava leaf extract emphasizes the necessity for specific improvements in the formulation.